Conventional receivers allow a user to monitor a particular selected broadcast frequency. Program material signals detected on the selected broadcast frequency can be indicative of one of the following: purely audio information; audio and text/data information; audio and video information; audio, video and text/data information; video and text information; or purely text/data information. The receiver decodes the detected signals and outputs the program material to an audio and/or video reproduction device. In each of these uses, a user can only monitor the particularly selected broadcast frequency to which the receiver is tuned. If the user is not satisfied with the program material, the receiver can be tuned to another frequency. That is, the user can only search for new program material by monitoring the receiver's current output.
U.S. Pat. No. 5,457,815 recognized the desire of a user to check other broadcast frequencies on a broadcast band for more desired/appropriate program material while simultaneously enjoying the program on one broadcast frequency. The disclosed system is based on the availability of a radio broadcast data system (RBDS). RBDS is a means by which radio broadcasters can transmit digital data along with their broadcast signal to “smart” receivers capable of performing a variety of automatic functions. Briefly, the RBDS signal is located on a subcarrier frequency of 57 kHz. The disclosed system's broadcast receiver is tuned to a selected broadcast frequency. A first of two RBDS receivers operates in a locked mode to receive RBDS data associated with the selected broadcast frequency. Simultaneously, the second of the two RBDS receivers operates in a scanning mode to scan RBDS data associated with all broadcast frequencies. Match criteria corresponding with one or more categorical portions of RBDS data is compared with the RBDS signal associated with each broadcast frequency scanned by the RBDS receiver operating in the scanning mode. Each time a match occurs, the broadcast receiver can optionally be switched from the selected frequency to the broadcast frequency on which the match occurred while the first and second RBDS receivers switch operating modes. However, this system is limited to a single (RBDS) broadcast band.
More recently, U.S. Pat. No. 6,011,854 disclosed an audio processing system that searches for information reports or updates (such as traffic, weather, time, sports, news and the like) broadcast over one or several radio stations. The search is based on at least one keyword (such as “traffic”, “weather”, “time”, “sports”, “news” depending on the desired report) being preselected by the user, and being entered into the audio processing system. Speech recognition software used by the audio processing system scan radio stations for the requested information report while the user may listen to other audio sources such as a CD or a tape. Once the requested information report is detected based on the entered keyword used in the radio broadcast, the audio processing system automatically switches its audio output to the radio station transmitting the desired broadcast. However, this system is limited to operation with conventional analog broadcast signals. The system also assumes that the user wants to switch over to the radio broadcast on which the match was found. Furthermore, the disclosure does not provide any teaching or suggestion as to how the user can listen to one radio broadcast while other radio stations are being searched.